Challa Ravi Kiran; Dr Sundresan, A(Cochin University of Science and Technology, June , 2015)
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Abstract:
Deep fat frying process is one of the widely followed cooking practices throughout the
world. Cooking oils serve as a medium for frying food for transferring heat and makes fried
food tasty and palatable. Frying process is a most complex process involving numerous
physicochemical changes which are complicated to understand. Frying leads to thermal
degradation of oil through thermo-oxidation, hydrolysis, and polymerization. Hydrolysis
results in formation of free fatty acids whereas oxidation process produces hydroperoxides
and small molecular carbonyl compounds. This whole process leads to the formation of polar
compounds and degradation of antioxidants that further degrades frying oil. Eventually,
through mass transfer process these degradation products accumulate into fried food and
reduce the nutritional quality of both oil and food. Thus, the frying process is of research
interest calls for detailed systematic study which is chosen for the present study. The primary
objective of this study is to understand the mechanism of degradation and characterization ofdegraded products which helps in arriving at the limits for frying oil utilization in terms of
number of frying cycles. The mechanistic studies and the knowledge on the degraded
products help to understand the way to retard the deterioration of oil for stability and
enhancement of frying cycles. The study also explores the formation of the predominant
polar compounds and their structural elucidation through mass spectrometry. Oxidation of oil
is another important factor that ignites the degradation phenomena. One of the best ways to
increase thermal stability of any oil is addition of potent antioxidants. But, most of the natural
and synthetic antioxidants are unstable and ineffective at frying temperatures. Therefore, it is
necessary to screen alternative antioxidants for their activity in the refined oils which are devoid of any added antioxidants. In this context, this study discussed the efficacy of several
natural and synthetic antioxidants to retard the formation of polar compounds and thermooxidation
during prolonged frying conditions. Similarly, the advantage of blending of two
different oils to improve the thermal stability was explored. The present study brings out the
total picture on the type of degradation products formed during frying and the ways of
retarding the determination to improve upon the stability of the oil and enhancement of frying
cycles.
Bindhu, C V; Harilal, S S; Nampoori, V P N; Vallabhan, C P G(Society of Photo-Optical Instrumentation Engineers, 1998)
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Abstract:
Thermal diffusivity measurements are carried out in certain organic liquids using the pulsed dual beam thermal lens technique. The 532 nm pulses from a frequency doubled Q-switched Nd:YAG laser are used as the heating source and an intensity stabilized He-Ne laser serves as the probe beam. Experimental determination of the characteristic time constant of the transient thermal lens signal is verified theoretically. Measured thermal diffusivity values are in excellent agreement with literature values.
V P N Nampoori; Santhi Ani, Joseph; Misha, Hari; Mathew, S; Gaurav, Sharma; Soumya; Hadiya, V M; Radhakrishnan, P(Elsevier, Journal of Optics Communications, October 6, 2009)
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Abstract:
Dual beam mode-matched thermal lens method has been employed to measure the heat diffusion in
nanofluid of silver with various volumes of rhodamine 6G, both dispersed in water. The important observation
is an indication of temperature dependent diffusivity and that the overall heat diffusion is slower
in the chemically prepared Ag sol compared to that of water. The experimental results can be explained
assuming that Brownian motion is the main mechanism of heat transfer under the present experimental
conditions. Light induced aggregation of the nanoparticles can also result in an anomalous diffusion
behavior.
Sankara Raman, S; Nampoori, V P N; Vallabhan, C P G; Saravanan, N; Mohammed Yusuff, K K(Springer, 1999)
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Abstract:
The thermal diffusivities of some polystyrene supported Schiff complexes of Co(II) and Cu(II) were determined by the laser induced photoacoustic technique. The effect of metal as well as the halogen part on thermal diffusivity of polymer supported complexes was studied. The thermal diffusivity of Co complexes increases while it decreases in Cu complexes with Cl, Br and I substitutions, respectively.
Achamma, Kurian; Unnikrishnan, K P; Sajan, D George; Pramod, Gopinath; Nampoori, V P N; Vallabhan, C P G(Elsevier, 2003)
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Abstract:
The wavelength dependence of thermal lens signal from organic dyes are studied using dual beam thermal lens technique. It is found that the profile of thermal lens spectrum widely differ from the conventional absorption spectrum in the case of rhodamine B unlike in the case of crystal violet. This is explained on the basis of varying contribution of nonradiative relaxations from the excited vibronic levels.
Achamma, Kurian; Unnikrishnan, K P; Sajan, D George; Pramod, Gopinath; Nampoori, V P N; Vallabhan, C P G(Elsevier, 2003)
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Abstract:
The wavelength dependence of thermal lens signal from organic dyes are studied using dual beam thermal lens
technique. It is found that the profile of thermal lens spectrum widely differ from the conventional absorption spectrum
in the case of rhodamine B unlike in the case of crystal violet. This is explained on the basis of varying contribution of
nonradiative relaxations from the excited vibronic levels.
Santhi, A; Kala, U L; Nedumpara, R J; Kurian, A; Kurup, M R P; Radhakrishnan, P; Nampoori, V P N(Springer, 2004)
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Abstract:
The fluorescence spectrum of the schiff base obtained from salicylaldehyde and 2-aminophenol is studied using an argon-ion laser as the excitation source and its fluorescence quantum yield (Qf) is determined using a thermal lens method. This is a nondestructive technique that gives the absolute value of Qf without the need for a fluorescence standard. The quantum-yield values are calculated for various concentrations of the solution in chloroform and also for various excitation wavelengths. The value of Qf is relatively high, and is concentration dependent. The maximum value of Qf obtained is nearly 0.78. The high value of the fluorescence quantum yield will render the schiff base useful as a fluorescent marker for biological applications. Photostability and gain studies will assess its suitability as a laser dye.
Achamma, Kurian; Sajan, D George; Bindhu, C V; Nampoori, V P N; Vallabhan, C P G(Elsevier, 2007)
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Abstract:
The effect of pH on the fluorescence efficiency of fluorescein is evaluated using thermal lens technique. Fluorescence efficiency increases as the
sample becomes more and more alkaline. But when fluorescein is mixed with rhodamine B fluorescence quenching of fluorescein takes place with
the excitation of rhodamine B. The electronic energy transfer in this mixture is investigated using Optical Parametric Oscillator as the excitation
source. The effect of pH on the efficiency of energy transfer in fluorescein–rhodamine B mixture is presented.
Bindu, J; Dr. Srinivasa Gopal, T K(Cochin University of Science and Technology., March , 2009)
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Abstract:
This study is the first of its kind in India, where in smoked and thermal
processed products have been developed using locally available wood as the
source of wood smoke and flavoring and a shelf life of one year has been
achieved. Retortable pouches of three layers, both imported and indigenous
were found suitable to store thermal processed products. Heat penetration rate is
quicker in retort pouches due to their thin profile in comparison to cans and
hence the total process time is lesser. The nutritional and sensory attributes of
the pouch products are better retained during processing. Hence these products
are more acceptable than canned products. lndian vegetarian food products and
fish curry products are available in the ready to eat form in the markets. Smoked
and thermal processed products have not gained an entry to the market and
hence this study will pave an opening for such products. Currently trade in tuna
products from India is meager compared to the global trade. ln India proper
utilization of tuna resources is yet to be achieved due to the lack of infrastructure
for handling and knowledge of value addition. The raw material cost is also less
due to the poor quality of the fish when landed. Hence, the availability of such
products will help in the trade of tuna products, improving the quality of raw
material landing and ultimately realizing a better value to the fishermen and
processors.
Jacob, Philip; Manjusha, M V(Taylor & Francis, 2008)
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Abstract:
The thermal transport properties, thermal diffusivity, thermal conductivity and specific heat
capacity of Dicalcium Lead Propionate (DLP) crystal have been measured following a modified
photopyroelectric thermal wave method. The measurements have been carried out with
thermal waves propagating along the three principal symmetry directions, so as to bring out the
anisotropy in these parameters. The variations of the above parameters through two prominent
phase transition temperatures of this crystal have also been measured to understand the variation
of these parameters as it undergoes ferroelectric phase transitions. In addition, complete
thermal analysis and FTIR measurements have been done on the crystal to bring out the correlation
of these results with the corresponding thermal transport properties. All these results are
presented and discussed. The data presented in this paper form a comprehensive set of results
on the thermal transport properties of this crystal.
Polytetrafluoroethylene (PTFE) composites
filled with Sr2Ce2Ti5O16 ceramic were prepared by a powder
processing technique. The structures and microstructures
of the composites were investigated by X-ray diffraction
and scanning electron microscopy techniques. Differential
scanning calorimetry showed that the ceramic filler
had no effect on the melting point of the PTFE. The effect
of the Sr2Ce2Ti5O16 ceramic content [0–0.6 volume fraction
(vf)] on the thermal conductivity, coefficient of thermal
expansion (CTE), specific heat capacity, and thermal diffusivity
were investigated. As the vf of the Sr2Ce2Ti5O16 ceramic increased, the thermal conductivity of the specimen
increased, and the CTE decreased. The thermal conductivity
and thermal expansion of the PTFE/Sr2Ce2Ti5O16
composites were improved to 1.7 W m21 8C21 and 34
ppm/8C, respectively for 0.6 vf of the ceramics. The experimental
thermal conductivity and CTE were compared
with different theoretical models.
Ramachandran, A; Sankar, T V(Society of Chemical Industry, November 26, 2004)
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Abstract:
The characteristics and stability of natural actomyosin (NAM) from rohu (Labeo rohita), catla
(Catla catla) and mrigal (Cirrhinus mrigala) were investigated. The total extractable actomyosin (AM)
was higher (7.60mgml−1) in the case of rohu compared with that from catla and mrigal (5mgml−1).
Although the specific AM ATPase activity was similar (0.43–0.5 μmolPmin−1 mgP−1) among the three
species, the total ATPase activity was lower in mrigal (25 μmol g−1 meat) compared with the other species
(37 μmol g−1 meat). The inactivation rate constants (kd) of AM Ca ATPase activity showed differences in
the stabilities of actomyosin among these fish, the actomyosin from catla being least stable. The NAM
from these species was stable up to 20 ◦C at pH 7.0. Catla AM became unstable at 30 ◦C, while rohu and
mrigal AM could withstand up to 45 ◦C. The thermal denaturation with respect to solubility, turbidity,
ATPase activity, sulphhydryl group and surface hydrophobicity showed noticeable changes at around
these temperatures
The thermal transport properties—thermal diffusivity, thermal conductivity and specific heat
capacity—of potassium selenate crystal have been measured through the successive phase
transitions, following the photo-pyroelectric thermal wave technique. The variation of thermal
conductivity with temperature through the incommensurate (IC) phase of this crystal is
measured. The enhancement in thermal conductivity in the IC phase is explained in terms of
heat conduction by phase modes, and the maxima in thermal conductivity during transitions is
due to enhancement in the phonon mean free path and the corresponding reduction in phonon
scattering. The anisotropy in thermal conductivity and its variation with temperature are
reported. The variation of the specific heat with temperature through the high temperature
structural transition at 745 K is measured, following the differential scanning calorimetric
method. By combining the results of photo-pyroelectric thermal wave methods and differential
scanning calorimetry, the variation of the specific heat capacity with temperature through all the
four phases of K2SeO4 is reported. The results are discussed in terms of phonon mode softening
during transitions and phonon scattering by phase modes in the IC phase.
Manjusha, M V; Dr. Jacob, Philip(Cochin University of Science and Technology, May , 2008)
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Abstract:
Photothermal spectroscopy is a group of high sensitivity methods used to measure optical absorption and thermal characteristics of a sample.The basis of photothermal spectroscopy is a photo-induced change in the thermal state of the sample.Light energy absorbed and not lost by subsequent emission results in sample heating.This heating results in a temperature change as well as changes in thermodynamic parameters of the sample which are related to temperature.Measurements of the temperature,pressure,or density changes that occur due to optical absorption are ultimately the basis for the photothermal spectroscopic methods.This is a more direct measure of optical absorption than optical transmission based spectroscopies.Sample heating is a direct consequence of optical absorption and so photothermal spectroscopy signals are directly dependent on light absorption.Scattering and reflection losses do not produce photothermal signals.Subsequently,photothermal spectroscopy more accurately measures optical absorption in scattering solutions,in solids,and at interfaces.This aspect makes it particularly attractive for application to surface and solid absorption studies,and studies in scattering media.
Description:
Department of Instrumentation,
Cochin University of Science and Technology
Mohanan, P V; Dr.Chandrasekaran,M(Cochin University of Science And Technology, August , 1995)
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Abstract:
Microbial enzymes are in great demand owing to their
importance in several industries such as brewing, baking,
leather, laundry detergent, dairy. starch processing and
textiles besides pharmaceuticals. About 80% of the enzymes
produced through fermentation and sold in the industrial scale
are hydrolytic enzymes. Due to recognition of new and new
applications, an intensive screening of different kinds of
enzymes with novel properties, from various microorganisms, is
being pursued all over the world. Bacillus sp are largely known to produce a-amylase, among the different groups of microoganisms, at industrial level. They are known to produce both saccharifying and liquefying a-amylases (Fukumoto 1963; walker and Campbell, 1967a). which are distinguishable by their mechanisms of starch degradation by the fact that the saccharifying asamylases produce an increase in reducing power about twice that of the liquefying enzyme (Fukumoto, 1963; Pazur and Okada, 1966). Under this circumstances, the present study was
undertaken, with a View to utilise a fast growing B.coagu1ans
isolated from soil, for production of thermostable and
alkaline oz-amylase under different fermentation processes
Description:
Department of Biotechnology, Cochin University of Science And Technology
Sugunan, S; Ramankutty, C G(American Chemical Society, 1995)
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Abstract:
The enthalpies of formation of charge-transfer complexes of benzene, chlorobenzene, and 1,3-dichlorobenzene
as donors with 7,7,8,8-tetracyanoquinodimethane as acceptor were determined. The thermochemical
data show an increased stability of charge-transfer complexes of donors with permanent dipole moment.
The results confirm the importance of electrostatic forces in bonding and stabilizing weak complexes.
The approximate formation constants of the complexes are also reported.